Prior art devices for sealing a rotating shaft are disclosed in U.S. Pat. No. 4,022,479 (Orlowski) and U.S. Pat. No. 5,024,451 (Borowski). Seal devices of this type may be used to prevent lubricant from escaping out of a bearing housing and/or to prevent contaminants from working their way into the housing. The prior art devices are formed of at least two ring-shaped members that rotate with respect to each other when the shaft is rotated. One of the members is fixed to the housing and does not rotate. The other member rotates with the rotating shaft.
The two ring members should be located very close together, particularly when the seal device is used to isolate the bearing from small particulate contaminants. Even small quantities of such contaminants are capable of significantly deteriorating the bearing. To prevent such contamination, the two relatively rotatable ring members must be held together very closely, with only a very narrow space therebetween.
The ring members of the Orlowski seal device are connected together by a separate securing means, not shown in the prior art patent. The ring members themselves have no means for establishing and maintaining a narrow spacing therebetween. Therefore, the prior art seal device cannot be manufactured as a unit with a preset, fixed spacing. The spacing between the ring members has to be set when the seal device is installed into the housing. This leaves room for human error outside the control of the device manufacturer. In particular, the Orlowski device can be improperly installed, with the ring members located too far apart to perform satisfactorily. Another problem with the Orlowski device is that the ring members may be separated subsequent to installation, for example by high pressure cleaning spray.
The ring members of the Borowski device are held together by a bead and a groove provided on the ring members themselves. The bead fits within the groove with an interference fit. This arrangement is an improvement over the Orlowski system in the sense that no separate securing means is needed. But the Borowski device is still unsatisfactory because the bead must be resiliently deformed to be positioned within the groove, and the groove must be correspondingly enlarged to receive the deformed bead. The deformation of the bead during assembly makes it difficult to achieve the desired close positioning between the two ring members, as explained in more detail below.
The disadvantages of the prior art are alleviated to a great extent by the present invention which provides a seal device including first and second ring members having connecting portions, with the connecting portion of the second ring member being located radially inside of the first ring member, and with the connecting portions being connected to each other by expansion of the first ring member relative to the second ring member.
In one aspect of the present invention, the connecting portions are connected to each other by heat-induced expansion of the first ring member.
In another aspect of the invention, the connecting portion of the first ring member is in the form of an annular recess, and the other connecting portion is an annular protrusion located within the recess.
In another aspect of the present invention, the seal device includes a third ring member for sealing the surface of a rotating shaft.
In another aspect of the present invention, the seal device includes a deflectable step for preventing the seal device from being forced from a bore during a grease application.
In another aspect of the invention, the seal device includes a passageway through which grease may flow under pressure during purging. An O-ring or other elastic member or garter spring may be provided for covering the grease passageway.
An object of the invention is to provide a unitized two piece labyrinth seal. Forming the seal of only two pieces is advantageous. A two piece seal may have fewer leakage paths than a three piece seal. Moreover, a two piece seal may be more economical to manufacture and more reliable.
Another object of the present invention is to provide a seal device that can be accurately assembled, with very little play.
Another object of the invention is to provide a high performance seal device that can be produced economically.
Another object of the present invention is to provide an improved method of assembling a seal device.
Yet another object of the invention is to provide a seal device that is especially well adapted for use in a grease environment.
Other objects and advantages of the present invention will become apparent from the following description and drawings which illustrate preferred embodiments of the present invention.